I'm uniformed military, but I work with civilians who need to dress the way you're going to need to dress.
I recommend getting a few pairs of chinos, in standard colors. Aim for pants that have hidden stitching, instead of khakis with visible stitching. No extra pockets. The legs can taper down, but don't get the 'skinny' version. Higher ankle length is okay-ish, but don't push it.
For shirts, get a few button downs or polo shirts. Get pastel colors, or patterned (no plaid!) if you like to register as feminine. Stick with regular colors if you don't mind registering as lesbian (though, CA, so maybe not?). You could branch out, and get a few blouse style tops, if you have the fashion sense for it. Just make sure they cover up a vast majority of your torso, and seem equivalent to having a collar in level of dressiness.
Get some sweaters, because no one likes being cold.
As a pro tip, iron whatever needs to be ironed. The dudes can be wrinkled, but will not be extended the same leniency.
If you truly only want to have this adventure every 2-3 years, I highly recommend going to Nordstrom's, or similar, and throwing yourself on the mercy of the clerk. It's what I've always done, and it really minimizes the pain.